Drilling for oil and gas with a rotary drilling rigs is being undertaken to increasingly greater depths both offshore and on land, and is an increasingly expensive operation given the demands to search for resources deeper into the earth, which translates into longer drilling time. In fact, it has been recently estimated that the costs to operate some rigs can exceed nearly half a million dollars per day. Thus a heavy emphasis is placed on procedures for reducing delays in the drilling operation.
Currently, one of the most regular delays in the drilling operation is the extension of the drill string. When a small part of the tubular string extends above the drilling deck, additional tubulars must be moved from a storage rack and connected with the upper end of the tubular string to continue drilling to greater depths. Today, top drive rotary systems are most often used in place of other, older technology (e.g., a rotary table to turn the drill string), because it allows the rig to utilize pre-assembled tubular stands. The creation and handling of tubular stands, independently of the drilling process, is a potentially important way to save time and money, since multiple strings of tubulars can be assembled offline which can cause less delays to the actual drilling operation.
Previous systems of handling tubulars and creating stands while conducting drilling operations have been described. See, for example, U.S. Pat. No. 4,850,439. However, such systems generally rely upon a hoist to lift the tubular and lack features to ensure the safety of the workers. Other systems utilized in manipulating tubulars have been disclosed in U.S. Pat. No. 6,976,540, U.S. Pat. No. 4,834,604, U.S. Pub. No. 2006/0151215, and U.S. Pat. No. 6,220,607. Generally, these handling systems, are heavy, costly, and consume a large amount of space. Moreover, these systems generally require significant human physical contact with the tubulars and lifting equipment at numerous times and locations, which can result in costly delay or possible injury. The alignment and transfer operations are lengthy and complex and the paths of the tubulars in the offline stand building are not fully restricted, which creates delay and safety hazards.
The industry continues to demand improvements in drilling technologies.